Extraction of biological molecules, for example, nucleic acids from biological samples such as blood, blood plasma, and tissue fragment is a fundamental important procedure in order to obtain test substances in industries involved with diagnosis, selective plant breeding for agricultural crops, food inspection, and the like as well as for research on life phenomena such as in biological, biochemical, and medical fields. Regarding nucleic acid testing, in particular, since PCR (Polymerasechain reaction) methods capable of DNA or RNA amplification have become common, demands for extraction of purified nucleic acids that can be amplified by the PCR method are increasing. In addition to the PCR methods, various nucleic acid amplification methods such as NASBA (Nucleic Acid Sequence-Based Amplification) methods, SDA (strand displacement amplification) methods, 3CR (self-sustained sequence replication) methods, TMA (transcription-mediated amplification) methods, Qbeta replicase amplification methods, and LAMP (Loop-mediated isothermal amplification) methods have been developed. Accordingly, application range of the nucleic acid testing is extending, and it is considered that demands for extraction of nucleic acids from biological samples will increase further.
Phenol/chloroform extraction has been known as a method of extracting nucleic acids such as DNA or RNA from biological samples. This method, however, has imposed serious burdens on workers due to the use of deleterious organic solvents or complicated procedures. In order to overcome the problem described above, a method of utilizing the property of nucleic acids to bind to silica or glass fibers in the presence of a chaotropic agent was proposed (e.g., Nonpatent Literature 1), and an automatic apparatus for performing nucleic acid extraction was also developed (e.g., Patent Literature 1).